Derer was reportedly last seen on Monday evening, according to the outlet.
His relatives reportedly filed a missing person report on Thursday afternoon and when police arrived at the residence where Derer visited, they saw things that made them suspicious, so they obtained a search warrant and soon found the body.
"They found what they thought was blood on the steps,” Philiadelphia Police Commissioner Richard Ross said, according to WPVI.
“And there were some other items that I don't want to get into right now. But it was something that led those officers when they first arrived to check on the well-being to determine that further action needed to be taken,” Ross reportedly added.
According to CBS Philly, Derer’s roommate and two others are being questioned by police.
The Associated Press contributed to this report.