On Wednesday, a memorial for Grimmer grew next to Main Street in Longmont, where the 16-year-old was hit.
For two days now, friends have come and gone from the memorial site to mourn.
"It's just too much to take in," Desire Gonzales, a friend of Grimmer, said.
Police say a fight between two groups of teens Monday night included racial name-calling. Grimmer was with a group of white friends, police say.
"There were some names exchanged, some racial tension. A group of white youth, a group of black youth," Commander Jeff Satur with the Longmont Police Department said.
Grimmer ran from the fight onto Main Street when he got hit. Police say they don't think anybody involved with the fight hit Grimmer with their car
"It was maybe an uninvolved third party that may have been distracted by the fight," Satur said.
Friends want to know who is responsible.
"I wish people would come forth and be honest with who hit him. Because we need some justice," Gonzales said.