Mass shootings where the shooter was never caught

I'll go ahead and start with one that happened in my own state, Illinois.

Lane Bryant shooting - The Lane Bryant shooting was an incident of mass murder and armed robbery at a Lane Bryant clothing outlet in the Brookside Marketplace in Tinley Park, Illinois, a suburb of Chicago, that occurred on February 2, 2008. The shooting resulted in five deaths and one injury.

Four customers, a part-time employee, and the store manager were taken to the back of the store and shot. Five of the women were killed; the part-time employee was wounded but survived. Police found the victims shortly after receiving an emergency call at 10:45 a.m. The gunman was described as a black man with thick, cornrowed hair and a receding hairline, along with one braid lying over the right side of his face at cheek level and decorated with four light-green beads on the end. Police believe it was a robbery "gone awry."

Info via Wikipedia

Simone Pianetti killed 7 people in Italy back in 1914 and managed to evade police and escape. He was never arrested and his body was never found.

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In 2009, an masked gunman killed 2 and wounded 15 at a Tel Aviv LGBT center before escaping on foot.
Despite an extensive manhunt, which involved the use of roadblocks and the closing of all LGBT related locations, the shooter was never caught. A few years later a couple of suspects were arrested and one was even indicted, but the charges were dropped after it was revealed that a crucial state witness lied.

Mass murderers who tried to get away:

William Unek escaped after committing his first murder spree in the Belgian Congo and almost remained uncaught until he committed his second one in Tanganyika Territory in which he was killed toward the end.

Abdulkadir Masharipov remained on the run for 16 days after the Istanbul nightclub shooting before being arrested.

Anis Amri was at large for 4 days after committing the Berlin truck attack before being shot dead in Italy.

Nickolas Cruz blended in with fleeing students and managed to get away from Stoneman Douglas before being arrested about a hour after his shooting.

Rizwan Farook and Tashfeen Malik managed to leave the Inland Regional Center but were promptly gunned down by police after engaging with them in a shootout.

Bruce Jeffrey Pardo planned to flee to Moline, Illinois to stay with a friend after committing his attack but his santa suit was stuck to him due to melting while he used a homemade flamethrower in his attack and couldn't be removed.

The perpetrators of the Marseille bar shooting.