DENVER (KDVR) Passengers on a Frontier Airlines flight leaving Denver for Houston restrained a man after he became combative and punched a window and seat 20 minutes after takeoff, according to the Houston Police Department.

The flight was Tuesday night and arrived in Houston about 11 p.m., a Houston police spokesperson told affiliate KDVR. Police said the man was “being combative” and started punching a seat and a window while the plane was in the air.

Several other passengers then helped restrain him. One passenger told Houston’s FOX 26 they used “shoestrings and belts, headphones” to restrain him.

A photo the station shared appeared to show the window’s inner panel broken, and the passenger told the station the passengers were restraining the man “so he didn’t break the second panel of the window.”

Once the plane landed, Houston police responded to a welfare check call on the plane. They also spoke to Frontier Airlines officials, but no charges have been filed, police said.

A Frontier Airlines spokesperson did not comment on the incident and referred KDVR to Houston police. They said the FBI is following up on the incident since it happened in air space.