In March 1993, Cullen broke into a co-worker's home while she and her young son slept, but left without waking them. He then began stalking the woman, who filed a police report against him. Cullen subsequently pleaded guilty to trespassing and received one year of probation. The day after his arrest, Cullen attempted suicide again. He took two months off work and was treated for depression in two psychiatric facilities, but attempted suicide twice more before the end of 1993. That September, a 91-year-old cancer patient reported that Cullen, who was not her assigned nurse, had come into her room and injected her with a needle. She died the next day. Her son protested that her death was not natural and Warren Hospital administered lie detector tests to Cullen and several other nurses, which Cullen passed. Cullen continued to work at Warren until the following spring.