LEESPORT, Pa. (AP) — A Pennsylvania man bought a gun one day after police responded to a domestic dispute at his home and used it less than three weeks later to kill his wife, three children and then himself, authorities said.

Megan Short, 33, told police she was afraid of her husband when they came to her home on July 18, investigators revealed Monday, and was in the process of moving out.

The bodies of Mark Short, 40, his wife and three children, 8-year-old Lianna, 5-year-old Mark Jr., and 2-year-old Willow were found Aug. 6 in the family's living room in Sinking Spring, about 50 miles northwest of Philadelphia.

The children — whom he had taken to an amusement park a day earlier for an employer-sponsored family day — were still in their pajamas. Their dog was also killed.

Megan Short was planning to move to an apartment in another town the same day as the killings, and her husband had supposedly planned to rent a moving van to help. Police broke into the home to check on the family after Megan Short's mother reported to police that her daughter had failed to show for a lunch date.

Relatives were left awaiting Megan Short's arrival at her new home.

Investigators found a handwritten murder-suicide note on the dining room table and a handgun near Mark Short, and an autopsy concluded Short's gunshot wound was self-inflicted.

Short appeared to have written the letter after he killed his family, acknowledging having bought the gun and using it to commit the murders, authorities said. But they declined to provide further details of what was in the letter.

District Attorney John Adams said the investigation also turned up a report of a domestic dispute at a Philadelphia hotel where the couple was staying June 4. He said only hotel security had been involved in that case.

Police who responded to the Short home a month later informed Megan Short how to seek a protection from abuse order, but although she said she intended to file the next day, she never sought such an order, the investigation found. Officers found the children home during the incident, but Mark Short had left the area before police arrived.

"I don't know that we know specifically as to why this relationship had disintegrated. We don't have any answers to that," Adams said. "Suffice it to say based upon our investigation ... we can tell you he was going through a breakup of a marriage and he was emotional about that, but that's all we can tell you."

Mark Short, a loan officer, had also been demoted at his job at the start of August, Adams said.

Megan Short had alleged in a Facebook post that she had been abused, a neighbor also said.

The Shorts had been featured in news stories about their difficulties getting medication for Willow, who had a heart transplant. Megan Short previously wrote that anxiety related to her daughter's condition had left her with post-traumatic stress disorder and "survivor's guilt" when children with similar problems from other families died.

Hundreds attended a funeral Mass for the family Friday. Mark Short was mentioned only in passing during the service.