Pagers, used every day by health care professionals, became a deadly weapon Tuesday as thousands of them simultaneously exploded in Lebanon.

Pagers used by the militant group Hezbollah simultaneously exploded, injuring more than 2,800 people and killing at least nine, officials said.

Chris Knayzeh was in a town overlooking Lebanon’s capital when he heard the rumbling aftershock of the 2020 Beirut port blast. Hundreds of tons of haphazardly stored ammonium nitrates had exploded, killing more than 200 people and injuring thousands.