GRESHAM, Ore. -- Gresham police officers began patrolling MAX trains Wednesday, just days after a brutal attack on a 71-year-old man.

Officers are only riding the MAX within Gresham's city limits. They are looking for illegal activity, inspecting for fares and providing a police presence on the trains.

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On Saturday night, a 15-year-old boy brutally attacked a 71-year-old man at the Gresham Transit Center, police said.

The attack came one day after Gresham Mayor Shane Bemis sent a letter to TriMet, informing the transit agency of the planned patrols.

In the letter, he said public intoxication, gang activity, assault, harassment and drug activity were "prevalent" on MAX trains.

The attack led TriMet officials to order additional security on the transit system, but Bemis said in the letter that "the time has come to take matters into our own hands."

Gresham Police Start MAX Patrols