Police in Gettysburg, Penn. arrested Samantha Elizabeth Unger, 23, after she confessed to having put bottles of Visine in her three-year-old son's drinks. Her son had to be airlifted to a hospital earlier this year after his heartbeat dropped to 40 beats per minute. Unger's one-year-old son also became sick after drinking from the three-year-old's poisoned cups.

According to the Hanover Evening Sun, doctors began to suspect that the children were being poisoned after both had been brought to the hospital multiple times in the same month:

Both children fell ill multiple times in March and the eldest had to be flown to the hospital March 21, according to court documents. Doctors at Hershey Medical Center told police that they believed the children were being poisoned after conducting several tests, the documents stated.

Investigators conducted interviews with the family and confiscated water bottles and sippy cups that they believed were making the children ill. Lab results showed that Tetrahydrozoline, better known as Visine, was present in the 3-year-old's urine sample that was taken at the hospital, according to the affidavit.

The Patriot-News reports that doctors informed police that Unger's three-year-old had enough Tetrahydrozoline in his system that it "created a substantial risk of death." Unger apparently told police that she would put more than one bottle of Visine in her son's drinks, but never kept track of exactly how much.

The mother is currently being held on charges of aggravated assault of children and endangering the welfare of children.

[Image via Patriot-News/Adams County Prison]