Martin Cobb, of Richmond, Va., was killed instantly when he was hit in the head with a rock at around 6:30 p.m. Thursday evening. Martin Cobb's family says the boy was trying to defend his sister from an attacker as they played near the train tracks in their back yard, according to WRIC-TV.
A 16-year-old male has been arrested in connection with the attack. The teen's identity has not been released because of his age, but he has been charged with murder and strangulation.
The 12-year-old girl is recovering in the hospital after the attack.
"We are deeply saddened by the tragic loss of one of our Redd Elementary School students, and extend our thoughts and prayers to the victim's family and friends," Martin Cobb's school said in a statement.
Neighbors have filed an official White House petition asking President Obama to formally recognize the boy's bravery, and a memorial fund has been set up in his honor.
Anyone with information is asked to call to contact Metro Richmond Crime Stoppers by calling 804-780-1000 or texting "iTip" followed by the tip to 274637.