A Tucson man is accused of lying to federal agents who were working to trace the gun used in a recent mass shooting that left a Pima County constable among the dead.

The arrest warrant for Josue Quintana says he bought a key part of the AR-15-style rifle, which authorities believe was used in a triple-murder suicide.

Among those fatally shot at a Tucson apartment complex was Constable Deborah Martinez-Garibay, who was trying to serve the alleged killer with an eviction notice.

Authorities say Quintana wrote on a federal form to purchase the rifle part that he was its actual buyer.

But when agents went through Quintana’s phone, they reportedly found an earlier message from the alleged killer telling Quintana to buy it for him.