Off-duty Philadelphia police sergeant Rafael Ali, 32, was driving "well above" the 35-mile-per-hour speed limit when his pickup truck slammed into a tree on Henry Avenue late Saturday night, killing the officer.
Capt. John Wilczynski, head of the police department's accident investigation district, told the Philadelphia Inquirer he thinks Ali fell asleep at the wheel, causing the crash around 11:45 p.m.
That theory is based on preliminary findings, Wilczynski said, and he could not rule out other factors.
"That's what our investigators are thinking, but of course we can't prove it," Wilczynski said.
There were no skid marks or signs of braking at the accident scene in the 6000 block of Henry Avenue in Roxborough, Wilczynski said, which supports the theory Ali fell asleep.