A Wisconsin man allegedly punched an elderly public bus driver dozens of times because he was “having a bad day” and believed the older man took his phone, authorities say.

Anthony Miller, 23, has been charged with battery to a public transit operator and physical abuse of an elderly person – intentionally causing bodily harm, according to Milwaukee County court records.

The incident occurred on July 18.

Miller is said to have exited a Milwaukee County Transit System (MCTS) bus at about 10:30 a.m. on the day in question, according to a criminal complaint reviewed by local Fox affiliate WITI.

According to the 72-year-old bus driver, the suspect “forced his way back onto the bus pushing in the door and began yelling at (the bus driver) asking where his phone was,” the charging document reads.

This passenger further “forced himself past the security plexiglass protecting (the bus driver) and began striking (the bus driver) in the face with a closed fist approximately 20 times,” the complaint goes on.

The driver is said to have suffered a 4-inch laceration on his forehead which later required four stitches, as well as pain and swelling all over his face and head. After the attack, the suspect left.

Milwaukee police reportedly arrived on the scene at Teutonia and Florist avenues shortly after, being told a bus driver was assaulted. Video surveillance helped detectives identify Miller as their suspect, authorities allege.

First, investigators had the account of the bus driver. Then came the suspect’s story. Miller was interviewed on Wednesday, WITI reported, where he admitted he was involved in an incident on a county bus. The attack apparently could be traced back to one thing: “he was having a bad day,” authorities wrote.

Miller reportedly described “having to come up with rent and having his car being stolen,” and once he exited the bus, he realized he dropped or forgot his phone and believed the bus driver had it.

The suspect allegedly told police “the bus driver assaulted him so he assaulted the bus driver back,” failing to remember how many times he hit the driver in total.

Miller was arrested on Wednesday and is being held on $5,000 bail. He has a preliminary hearing scheduled for Aug. 25.