"The suspect approached the man and, without provocation, struck him in the face several times," police said in a press release.
It's unclear if the victim suffered any serious injuries in the assault.
Police said after the man was hit in the face, "a struggle ensued resulting in the victim's bag falling to the floor of the bus."
The suspect allegedly then stole the victim's bag and got off the bus. According to police, he was last seen going south on Martin Grove Rd.
The suspect wanted in a random assault on a TTC bus. Toronto Police Service
TPS has since released a security image of the suspect, describing him as a man in his 40s, approximately 5'11" with black hair and a black and grey beard. Police added the man was also last seen wearing a red t-shirt, black shorts, and black shoes.
Investigators have asked anyone who witnessed this assault or who might have further information on the incident to contact them at 416-808-2300, or Crime Stoppers anonymously at 416-222-TIPS (8477), or at www.222tips.com.
News of another random attack on the TTC followed the unprovoked murder of a 16-year-old boy at a subway station last month.
However, in a recent report from the TTC, the transit agency said incidents on public transit had seen a decrease, noting a drop in incidents from January to February when TPS officers were brought in to beef up security across the transit network.
Still, in the month of February, a total of 111 "offences against customers" were reported.
The alleged suspect in the assault with a weapon investigation. Toronto Police Service