Allen had been married to Spiller's maternal grandmother until she passed away when Spiller was in eighth grade, according to the Buffalo News.
Spiller played in Buffalo's 30-7 preseason loss to the Redskins on Saturday, the day of the shooting.
"I talked to him when we landed from the Washington game," coach Doug Marrone said. "I obviously excused him to be able to go back and handle obviously what is a personal situation. Our thoughts and prayers go out to the victims as well as C.J. and his family in this situation."
Due to the sensitivity of the situation, Marrone hasn't put a timetable on Spiller's return.
"I don't have any answer of when he's going to come back," Marrone said. "We're in communication just making sure that we're there to support him, that he's doing well and then obviously we're monitoring of when he needs to come back. We want to make sure that he handles what he needs to handle."
According to the Buffalo News, Allen was a key male figure in Spiller's young life.