Hospitals aren't designed to protect against a gunman trying to enter the building to take lives.

A shooter killed four people, then shot himself in the head Wednesday at a Tulsa hospital. Authorities said that the attacker gained entry to a Saint Francis Hospital building with minimal difficulty, hours after purchasing an AR-style rifle.

Here are some facts about security at Tulsa and American hospitals.

DID THE GUNMAN HAVE to PASS THRU SECURITY

Authorities said that Michael Louis, 45, from Muskogee, Oklahoma was the shooter. He parked his car in an adjacent garage and then entered the medical building through the unlocked doors.

Tulsa Police Chief Wendell Franklin stated Thursday that the entry is open to all. "He was able walk in without any kind of challenge."

It was only a short distance from the entrance to Phillips' office, where Louis shot and killed his primary target, Dr. Preston Phillips. Police claimed Phillips had recently performed surgery on Louis, and that Louis blamed Phillips for the chronic pain he still suffers.

Franklin stated that Louis entered the building and "he started firing at anyone in his path." At least one person who was holding the door open for others to escape was shot and killed.

COULD BETTER SECURITIES HAVE TERMINATED THE SHOOTER

Saint Francis Health System's president and CEO stated that guns can be used to cause harm.

Dr. Cliff Robertson didn't provide any details regarding hospital security. Although he stated that the hospital has procedures for dealing with "difficult and unhappy patients", he didn't elaborate.

Officials at hospitals planned to examine their security procedures over the coming days. Robertson stated that there would be "a thousand questions" about the shooting.

Official accounts state that officers responded quickly to the shooting. Wendell stated that officers responded within minutes to the shooting and that the shooter died as police approached.