ROCKVILLE, Md. — The day after Montgomery County Executive Isiah “Ike” Leggett announced there would be an investigation into the cause of a 911 outage on Sunday night, Montgomery County council members are still shaking their heads over the incident.

“It’s shocking,” said Council President Nancy Floreen. She was referring to initial information from the county executive’s office that said the outage was the result of the failure of air conditioning equipment that served a backup system. That backup system was in use while the county’s primary 911 system was undergoing an upgrade.

“It’s hard to believe that having a backup system go out could take out the whole system,” she said.

Councilman Sidney Katz, the former mayor of Gaithersburg, said it was unclear to him how the county could rely on a single 911 system without added backups.

“There should be redundancy on top of redundancy,” Katz said.

The county executive’s office noted that the outage occurred during a period when calls often come in at a lower rate. The outage spanned from 11:10 p.m. Sunday to about 1:10 a.m. Monday.

Councilman Marc Elrich, chairman of the council’s public safety committee, said the outage “should have never happened.”

“I don’t care what time of the day it is and I don’t care how few people need the service, the fact is that this is a life-or-death service,” Elrich said.

Leggett’s office is investigating the outage and reports that two deaths occurred during the period that 911 was unavailable. It’s not clear whether those deaths were directly related to the outage.