(NewsNation) — Texas authorities on Sunday continued their search for a man who escaped prison after stabbing a transport bus driver in a rural county between Houston and Dallas.

Gonzalo Lopez, 46, was serving a life sentence after being convicted in the 2005 slaying of another man along the Texas-Mexico border. Officials say Lopez killed the man with a pickax.

He escaped custody in Leon County Thursday while on a bus headed to a medical appointment in Huntsville.

Officials don’t know how, but Lopez was able to get out of his restraints and gain access to the driver’s compartment of the bus, said Robert Hurst, spokesperson for the Texas Department of Justice and Department of Corrections.

There was a struggle between the officer driving the bus and Lopez, during which Lopez stabbed the driver in the hand. The officer subsequently pulled the bus over to the side of the road. Lopez and the driver then got out of the bus and continued fighting, when another officer, who had been in the back of the bus with a shotgun, fired two shots into the bus’ rear tires, Hurst said.

It was then that Lopez got back on the bus. He drove about another mile down the road with flattened back tires until he lost control of the bus. Officers caught up to Lopez and fired shots at him as he ran across a cow pasture.

“We don’t think he got hit,” Hurst said.

There were 15 other inmates on the bus, but no one else escaped, Clark said. Hurst said he could not comment on whether Lopez planned this escape.

Hurst said Lopez was searched before getting on the bus.

Jack Donson, who worked for the Federal Bureau of Prisons and now has a consulting business, said some strip searches are lax, and getting out of restraints does happen.

“It’s definitely unusual for him to get out of the restraints and have some kind of an object to get to the driver,” he said on “NewsNation Prime.”

An investigation into how Lopez got out of his shackles and handcuffs, and took over the prison bus is underway, law enforcement said.

The Centerville Independent School District, which is near where Lopez escaped, was closed as an extra precaution Friday. Residents in the area are being told to lock their doors and vehicles.

“If you spot Lopez, immediately contact 911 and do not approach him,” the Texas Department of Criminal Justice said on Facebook.

NewsNation local affiliate KXAN reported that Lopez was added to the Texas 10 Most Wanted Fugitives List

Hurst said the FBI, the U.S. Marshals Service and several local law enforcement agencies are trying to find Lopez.

On Saturday, authorities focused their manhunt near Centerville, Texas, though said Lopez could have made it out of the area.

The Texas Department of Criminal Justice is offering a $15,000 reward for information leading to Lopez’s capture and arrest. Crimestoppers added $7,500 to the pot Friday for a total of $22,500.

The Texas Department of Criminal Justice is temporarily suspending visitation at some locations throughout the state as more than 300 officers work to capture Lopez, Hurst said.

“We want to make sure we’ve got the proper staffing on our units,” he said.

Anyone with plans to visit a Texas inmate over the weekend should contact the warden’s office and ask if visitations will be allowed.

This story is developing. Refresh for updates.