Although the medical examiner ruled the official cause of death as drowning, family and friends say many questions remain unanswered.
Evanston police plan to look at the interviews already conducted in the investigation, as well as Maddula's cell phone records, in hopes of finding the answers.
Meanwhile, Maddula's family remembered him at a campus gathering-- and also asked students for help.
"If you know anything, please come forward and help us give Harsha the justice he deserves," said Kumar Rachuri, cousin.
Northwestern staff and students shared memories of the pre-med, honor roll student.
"Rest in peace, Harsha. I miss you already," said Linzy Wagner, from the university's public affairs residential college.
"I pray for him all week. I continue to pray for him. May his memory be a blessing," said Morton Shapiro, Northwestern University president.
For some students, the vigil helped to bring the community together after a distressful week.
"It's a great act of solidarity that has brought a campus together that has honestly just been confused," said Harsh Shah, student.
Maddula, a diabetic, left a party early Saturday morning and was found dead in Wilmette Harbor on Thursday.
"Something happened at this party. We know something happened. But the issue is right now is, how do we find out these answers," said Sushma Maddula, cousin. "Who was Harsha with last? Who did he speak to last? I still do not know. These are answers that need to be answered. The students need to speak up."
Police say Maddula's phone, wallet, and money were on him. And cell pings tracked the phone at a walking pace to the harbor.
"We are looking at everything with an open mind. There is obviously medical concerns. Other issues have come up-- alcohol consumption. We're looking at every angle," said Commander Jay Parrott, Evanston police.
Evanston police say they do not suspect foul play, but they're continuing their investigation because they want to give Maddula's family as many answers as possible.