More has also been learned about the three young people killed - Brian Fraser, Alexandria Verner and Arielle Anderson.
Slain students were 'incredibly loved,' 'tremendous' leaders
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Vigils are being held across the country, from East Lansing, to the victims' hometowns, to north suburban Highland Park, which had its own mass shooting during a Fourth of July parade last year.
A vigil was held on MSU's campus Wednesday.
"I always thought that it could happen anywhere; I never thought it would happen here," one student said.
Classes are canceled, and Michigan State University is operating with only essential employees on campus while the investigation into the shooting continues.
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School officials said they plan to offer counseling to students, faculty and staff to allow for everyone to process what happened.
A vigil on the campus of MSU Tuesday night honored the victims of another rampage.
The three students killed were sophomore Brian Fraser, president of his fraternity; junior Alexandria Verner, a popular athlete known for her kindness; and Arielle Diamond Anderson, a junior who wanted to become a surgeon.
"We start calling and texting, and no responses were coming. So we were just hoping that maybe she was hiding somewhere. We want the senseless killing to stop," Anderson's aunt Kimella Spivey said.
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All three students who were killed came from the suburban Detroit area. The names of the five who were injured have not been released.
Among those killed was Alexandria Verner, a junior from Clawson, whose LinkedIn profile said she was studying integrated biology and anthropology.
A 2020 graduate of Clawson High School, Verner "was and is incredibly loved by everyone," district Superintendent Billy Shellenbarger said in a statement Tuesday. "She was a tremendous student, athlete, leader and exemplified kindness every day of her life.
"If you knew her, you loved her and we will forever remember the lasting impact she has had on all of us," Shellenbarger said, adding that Verner's parents, sister and brother were "grieving but are certainly already feeling the uplifting support of this tremendous community. "
Verner's Twitter bio says, "Can't stop dreaming," and features photos and videos from Clawson basketball and volleyball games.
Hundreds of mourners flowed onto a suburban Detroit high school football field Tuesday night to light candles and reminisce about Verner in a vigil led by Shellenbarger.
Those in attendance also observed a 24-second moment of silence in honor of Verner, who wore jersey No. 24 while she was a basketball player at Clawson High.
"While you are silent," Shellenbarger said over the public-address system, "think about her smile, think about that hero that was among us for 20 years."
Also killed was Brian Fraser, a sophomore who attended Grosse Pointe South High School.
Fraser was president of Michigan State's chapter of Phi Delta Theta fraternity, which said in a statement Tuesday that its members were "heartbroken."
"Brian was our leader, and we loved him," the fraternity said. "He cared deeply about his Phi Delt brothers, his family, Michigan State University, and Phi Delta Theta. We will greatly miss Brian and mourn his death deeply as our chapter supports each other during this difficult time."
University police identified the third victim as Arielle Anderson, a junior who graduated from Grosse Pointe North High School.
"As much as we loved her, she loved us and others even more," her family said in a statement. "She was passionate about helping her friends and family, assisting children and serving people." They described her as "sweet and loving," with an "infectious smile."
Anderson was pushing to graduate early from Michigan State, hoping to become a surgeon as quickly as possible, the statement said.
"We are absolutely devastated by this heinous act of violence upon her and many other innocent victims," her family said.
Jon Dean, superintendent of the Grosse Pointe schools, mourned the loss of his district's former students in an open letter.
"I can't even process what I just wrote," Dean said. "It is with a great deal of sadness that I bring this news to you and my thoughts go out to the many families that are suffering from another senseless act of violence."
There's also a clearer picture emerging of the suspect, who police said took his own life.
Authorities said 43-year-old Anthony Dwayne McRae died of a self-inflicted gunshot wound hours after opening fire in two buildings on campus.
Detectives said a note found on McRae listed other locations he wanted to attack in Michigan, Colorado and New Jersey.
RELATED | Some MSU students critical of text message from school during shooting
Investigators are still working to determine a motive, and said McRae had no connection to the victims or the university. He did have a history of mental illness and was described as a loner.
Records show he also served 18 months in prison for a weapons charge, beginning in 2019.
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Michigan State student Jackie Matthews is from Newtown, Connecticut. She was in sixth grade when a gunman killed 20 students and six educators at Sandy Hook Elementary in 2012.
After the shots rang out Monday night, she said she was once again a witness to carnage.
"The fact that the odds of me being in both of those places for two mass shootings is unfortunately not as unlikely as it is, for other people as well. Enough is enough. It just needs to end," Matthews said.
"Good Morning America" spoke with Matt Riddle, whose daughter, Emma, not only survived the MSU mass shooting, but, just 14 months ago, was nearly a victim in another mass shooting at a high school in Oxford, Michigan, that left four dead and injured seven.
"Having been through it in Oxford, it helped her understand what she needs to do in these situations. And, I don't like that she has those tools. I wish she didn't, but she does," Riddle said.
Classes at MSU will resume Monday.
Five students remain hospitalized in critical condition. During a news conference Wednesday, officials said a number of the students injured are international students.
Those who left items in the buildings where the shootings took place can access them Wednesday, FBI officials said.
Some Michigan State students channeled grief into protest Wednesday, gathering at the capitol in Lansing to urge gun reform.
Hundreds braved cold and windy weather as they sat on the building's majestic steps, listening to sympathetic and angry speeches calling for legislative action to curb the violence they have been exposed to.
They were joined by more from the Spartan community as they moved to the path leading to the entrance and conducted a "sit in" there.
Student leaders then addressed the protest with more tearful pleas for change and accounts of the trauma they've experienced.
ABC News contributed to this report.