Authorities in Texas believe a 34-year-old nurse was responsible for the deaths or injuries of at least seven patients after he injected air into their catheters at a Tyler hospital.

William George Davis was indicted recently on capital murder charges, about two months after he was indicted on counts including murder and aggravated assault.

In that case, he was charged in connection with 47-year-old heart patient Christopher Greenway’s death.

The incidents occurred at Christus Mother Frances Hospital between November and January, as reported by Fox News.

A statement following the latest indictment indicated that the hospital is “working in concert with the Tyler Police Department” and is “reviewing patient files since the beginning of Will Davis’s employment.”

As part of their investigation, police determined that Davis used “unnecessary and/or inappropriate” methods in connection with the two victims whose conditions devolved after an interaction with him.

Investigators also say he had not been assigned to care for the victims, as previously reported by CrimeOnline.

In the later case, he is accused of turning off an alarm attached to one victim’s IV in addition to other efforts to cover the evidence.

Three alleged victims began exhibiting signs of distress just minutes after he left their rooms, according to court records.

Davis remained behind bars with bond set at a total of $4 million as of the latest reports available.

He is expected to face trial in December.

[Featured image: William George Davis/Smith County Jail]