PASCO, Wash. (CBS/AP) A man accused of stabbing his girlfriend to death Monday in the eastern Washington city of Pasco was deported to Mexico three weeks earlier, but somehow made his way back to the U.S. to commit the crime, authorities say.

Franklin County Superior Court documents say Gregorio Luna-Luna had been jailed from January to March for alleged domestic violence, and then was held at the Northwest Detention Center in Tacoma until he was deported on May 1.

Police say the 31-year-old returned to Pasco and killed his ex-girlfriend, Griselda Ocampo Meza, who was mother of his 5-year-old-son. An autopsy revealed that it was a single stab wound to the chest that killed the 21-year-old woman.

The accused killer had several citations for assault going back at least two years, reports CBS affiliate KEPR, which says Luna-Luna ignored the citations and never showed up in court. He became a high priority for authorities after he kidnapped his own son and police issued an Amber Alert. When the two were found, Luna-Luna was thrown in jail.

KEPR was told by an immigration spokesperson that Luna-Luna bonded out and US Immigration and Customs Enforcement  (ICE) took him into custody. He sat in an ICE detention center until late April when a judge said he should be deported. Within two days he was in Mexico, but not necessarily in jail.

Immigration officials couldn't specifically say what the Mexican authorities did when he arrived. But somehow Luna-Luna made it to the Tri-Cities area of southeast Washington in a matter of weeks. Franklin County prosecutor Steve Lowe told KEPR, "It takes about 10 to 12 days by foot to get back to Tri-Cities (from Mexico). it's not unusual. Frustrating, yes, we obviously have a border problem."

Luna-Luna is in the Franklin County jail and has not yet been charged in Meza's killing. KEPR reports that prosecutors may go for first degree murder and make it a death penalty case.