It appears that Luigi Mangione, 26, of Towson, Md., is the person of interest in UnitedHealthcare CEO Brian Thompson’s killing.

He was detained Monday in Altoona, Pa., after a manhunt. According to the Times, Mangione had a manifesto criticizing the healthcare industry.

Mangione is in custody in Altoona, Pennsylvania, where police said he had a gun thought to be similar to the one used in the killing of UnitedHealthcare CEO Brian Thompson, according to the NYPD.

Citing a law enforcement official, The Associated Press reported that along with the gun, authorities also found a silencer, fake IDs and writings that appeared to be critical of the health insurance industry, according to the law enforcement official.

Thompson, 50, was killed Wednesday in what police said was a “brazen, targeted” attack as he walked alone to the Hilton from a nearby hotel, where UnitedHealthcare’s parent company, UnitedHealth Group, was holding its annual investor conference, police said.