BERLIN (AP) — German authorities are looking into the history of a Polish nurse suspected of killing and robbing a patient to see if he had any other victims.

Munich police have arrested 36-year-old Grzegorz Stanislaw Wolsztajn on suspicion of killing an 87-year-old retiree with insulin shots in February. Police say Wolsztajn confessed to stealing about 1,210 euros ($1,500) and two debit cards from the victim.

At least four other former patients were hospitalized with life-threatening conditions.

News agency dpa reported Wednesday that investigators have received 26 tips on the suspect's past jobs as a nurse across Germany after releasing his picture and asking the public for help.

The case echoes that of a German nurse serving a life sentence for two murders who was in January charged with killing 97 other patients.