Out of nowhere: bus passenger on the run after assault

Shocking footage has emerged of a bus passenger allegedly knocking an older man to the ground in a violent, random attack.

The 72-year-old victim was boarding a bus in Osborne Park, Perth just before 1pm on May 12 when the alleged offender ploughed into the man and knocked him to the ground.

The alleged offender was seen calmly boarding the bus before the driver and other passengers rushed to the injured man's aid.

The 72-year-old was helped to his feet after sustaining cuts and grazes to his arm.

The alleged offender, described as being between 20 and 30-years-old with short dark hair and a medium build, left the area on foot shortly afterwards, police said.

Investigators continue to search for the alleged offender and are calling for public assistance in identifying the man.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or report online at crimestopperswa.com.au