OMAHA, Neb. (AP) — The man accused of killing an Omaha police officer this week had been linked to two other violent crimes in recent years, but officials say they lacked evidence to prosecute him.

Marcus Wheeler was killed by police on Wednesday after police say he shot 29-year-old Officer Kerrie Orozco.

In 2012, Wheeler was accused of shooting at a car. One of the occupants, Erica Jenkins, identified Wheeler as the shooter. But charges against Wheeler were dropped after Jenkins was implicated in three 2013 murders. Prosecutors say that discredited Jenkins as a witness against Wheeler.

In 2007, Wheeler told police he had disposed of a gun in a 2007 double homicide. But because authorities couldn’t determine the shooter, prosecutors couldn’t charge Wheeler as an accessory.