Investigators have since learned Tolman went to the second apartment intending to kill a third victim, a man who was visiting his parents that night, Peterson said.
"We believe that saved his life," Peterson said.
Investigators are not certain what Tolman's relationship was with Madden, but they believe the shooting was motivated by his disapproval of her contact with other men, Peterson said. Tolman had been friends with Sadler and the third intended victim, Peterson said, and while the nature of Madden's relationship with either of those men was not known, Tolman was angry about it. Police said Tolman had been exchanging text messages with Madden shortly before the shootings but would not release details.
He also left a suicide note in his apartment.
"It just said, 'I'm sorry' and 'I'm being very selfish,'" Peterson recounted.
Tolman was in the Utah National Guard, according to Lt. Col. Stephen Fairbourn.
Tolman had been a member of the Guard for five years, and was a laundry and equipment technician, Fairbourn said, adding that the man had never been deployed.
"We certainly feel the loss," Fairbourn said. "We send our condolences to all of the families of all that are affected. We are supporting and assisting in the investigation as much as possible."
Logan police were familiar with Madden, who held an internship with the department as a Utah State University student majoring in sociology and minoring in criminal justice. Coincidentally, her assignment included researching "active shooter" response policies used by other police agencies.
"I worked with her at that time and found her to be an absolutely astounding young lady," Franke said. "She was dedicated and committed to making other people's lives better. We're just shocked and saddened by this terrible loss."
Franke did not know Sadler, except that he was "an acquaintance who was visiting" Madden.
Police were reluctant to describe Tolman and Madden's relationship as romantic.
"We're just saying that they were acquaintances, were communicating with each other at various times, and had some sort of involvement," Franke said.
Madden was registered for classes at USU this fall, according to university spokesman Tim Vitale.
Vitale said Tolman had just graduated in May from USU with a degree in political science.
Sadler worked as a manager at Todd Sadler Construction, according to an online profile.
He graduated from Logan High School in 2007, and classmates on Monday created a page on Fundingjar.com to help cover funeral costs and support his family. The John Sadler fund had raised more than $1,800 as of Monday night.
"Johnathon was an incredible person, such a sweet and bright spirit, and I grieve for his family and those who feel his loss today," said longtime friend Patrick Risk.
Police could not further discuss details of the case, but Franke did say they believed all parties involved have been accounted for, and no other victims or suspects are known.
Tribune reporter Jessica Miller and The Associated Press contributed to this story.