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.

CNN has reached out to Jeziorski’s ex-wife for comment.

Police said Jeziorski had no criminal record in Greece.

Eyewitnesses described seeing a masked man in black who approached the victim on foot, with one telling local media that she heard about six shots and saw the perpetrator run from the scene.

“There was no silencer on the gun, it was very loud. It was like an explosion,” another eyewitness who saw the attack told CNN affiliate CNN Greece.

The family is raising money to repatriate his remains to his native Poland, and to pay for legal representation in Greece “to pursue legal action and support ongoing investigations.”

“Our family is heartbroken, and we are doing everything we can to ensure that justice is served,” his brother Lukasz Jeziorski wrote on the online fundraising page.

UC Berkeley said in a statement that Jeziorski “had a passion for teaching” and during his 13 years there taught data analytics skills to more than 1,500 graduate and PhD students. He was described by friends and coworkers as “an amazing person, friend, and colleague” as well as “exceptionally gifted and hard-working.”

“I am heartbroken by news of the tragic and sudden death of Professor Przemyslaw Jeziorski, a beloved member of our marketing faculty and Haas community,” said Jenny Chatman, dean of UC Berkeley’s business school, in the statement. “While authorities are investigating what happened, our focus is on supporting our community during this difficult period. My heart goes out to Przemek’s family and loved ones. We will miss him.”

The highly acclaimed economist created a popular MBA marketing analytics course and “became a leading expert in quantitative marketing, industrial organization, and the economics of digital markets,” according to Berkeley.

His research on subsistence-level entrepreneurs and financial inclusion and training took him around the world, with one colleague describing him as “truly adventurous.”

“He was a loving father of two young children and always there if someone needed help,” Berkeley Professor Zsolt Katona said in the statement. “He had great influence on the marketing field not only through his research but through his energetic presence and optimism combined with a healthy dose of skepticism.”

Before joining the staff at Berkeley, Jeziorski worked as an assistant professor of economics at Johns Hopkins University and a visiting scholar at Microsoft. He obtained his PhD in economic analysis from Stanford and earned master’s degrees from the University of Arizona and the Warsaw School of Economics in Poland.

Jeziorski had been published in multiple top-tier academic journals, including the American Economic Journal and the RAND Journal of Economics. He was also the co-founder of a start-up called Keybee, a short-term rental property management platform. (CNN, but headline rejigged)

• PHOTO: Przemyslaw Jeziorski, 43, an economist and professor of marketing at UC Berkeley, was shot multiple times on July 4 in a suburb of Athens. Lukasz Jeziorski/Why Donate