The Broward County Sheriff's Office is changing the way it responds to shootings in the wake of the Parkland, Florida, school massacre that killed 17 people, according to a letter by Sheriff Scott Israel.

The letter, addressed to the Pinellas County Sheriff Bob Gualtieri, who is the chair of the Marjory Stoneman Douglas High School Public Safety Commission, outlined changes the department has adopted since the Feb. 14 shooting, including additional training and language changes that make officers' response to shootings less ambiguous.

Part of the change says an officer responding to a shooting "shall" intervene in a situation in order stop the attacker, according to the letter, which was obtained by NBC News. Previous language, according to the Miami Herald, said an officer "may" intervene.

Broward County Sheriff Scott Israel speaks before the start of a CNN town hall meeting in Sunrise, Florida, on Feb. 21, 2018. Michael Laughlin / Reuters

The new policy also includes an updated list of priorities for officers responding to a shooting scene:

“Deputies responding to active threat(s) incidents shall attempt to protect the life of innocent persons through immediate tactical intervention to eliminate the threat. In such scenarios, the prioritization of activities in order of importance will be: 1. Stop the active assailant(s); 2. Rescue the victims; 3. Provide medical assistance; 4. Arrest suspects and preserve the crime scene."

The new policy notes rare exceptions to this rule.

"While deputies are expected to tactically intervene, there may be very limited extenuating circumstances when entry by a solo deputy must be delayed until the situation changes, or additional deputies or resources are present," it reads.

Additionally, since the Parkland shooting, the nearly 1,400 Broward Sheriff's Office deputies have completed 8 hours of additional, scenario-based "active shooter" training, according to the letter.

"Be assured, the reforms adopted to date are not the end of this process. Rather, they are a midway point we continue working towards addressing all of the findings related to our agency and implementing all of the Commission’s recommendations," the letter reads.

Margarita Lasalle, from right, the budget keeper, and Joellen Berman, Guidance Data Specialist, look on at the memorial in front of Marjory Stoneman Douglas High School as teachers and staff are allowed to return to the school for the first time since the mass shooting on campus on February 23, 2018 in Parkland, Florida. Joe Raedle / Getty Images file

Ryan Petty, a commissioner on the safety panel and the father of Alaina Petty, 14, who died in the Valentine's Day shooting, has called on Israel to resign, saying the sheriff's leadership has been a failure.

Petty told NBC News on Wednesday that Israel was the person who originally wrote that officers "may" enter an active shooter situation, rather than "shall."

"It’s an admission of responsibility without coming out and saying, 'I made a mistake," and leaders admit mistakes," Petty said of Israel's reversal.

Petty, who said he hadn't seen the entire document sent by Israel, said the number of deputies who did not engage with and ultimately stop the gunman is reflection on the previous poor policies.

"This should have been in place before Feb. 14," he said.

The letter also notes that an internal investigation has been launched into Sgt. Brian Miller and Deputy Edward Eason. Earlier this year, body camera footage showed that both men delayed entering the building where the shooter had opened fire, according to the Associated Press.

The officers were suspended last month, according to the AP, but in documents from Broward Sheriff's Office dated Dec. 4, it appeared both men have since been placed on restrictive administrative duties.

Former MSD student Nikolas Cruz, now 20, has pleaded not guilty to the shooting, although his lawyers have said he would plead guilty in exchange for a life sentence. Prosecutors are seeking the death penalty.