Police in Greece are searching for the killer of a University of California Berkeley professor who was shot dead on July 4 while visiting Athens to see his children and attend a family custody hearing.

Przemyslaw Jeziorski, 43, an economist and professor of marketing at UC Berkeley’s Haas School of Business, was shot multiple times at close range in a residential suburb of Athens and died at the scene, according to police.

A masked gunman “approached the victim on foot and opened fire from close range” at about 4:15 p.m., hitting the victim in the neck and chest, according to police spokesperson Konstantina Dimoglidou. Seven bullet casings from a 9mm caliber firearm were found at the scene, police said.

A murder investigation is underway. With the suspect still at large more than a week later, his family and friends are demanding police intensify their efforts.

The shooting happened near the home of Jeziorski’s ex-wife in the suburb of Agia Paraskevi, one day after the father-of-two attended a custody court hearing, police said.