Dallas police officers have lined up in a silent salute outside the hospital where several of their colleagues remain in critical condition after snipers killed five officers at a Black Lives Matter march.
At least seven were injured after four snipers opened fire on police from a garage during a Black Lives Matter demonstration in the Texan city on Thursday evening.
The officers guarding the hospital raised their hands in the customary salute of respect to honour their fallen colleagues.
The shooting has been called the deadliest day for law enforcement officers since 9/11.
Three suspects are in custody with the fourth reported to have shot himself after an hours-long standoff.
Sniffer dogs are being led into the garage near El Centro college to search for explosives after the suspect reportedly told police "the end is coming" and "there are bombs all over the place in this garage and downtown".
Two of the dead officers have been named on social media as Patrick Zamarripa and Brent Thompson.
The Dallas police department paid tribute to its fallen officers saying it was "a devastating night" when they confirmed the fifth officer had died.
The protest was against the police shooting of two black men - Philandro Castile and Alton Sterling - in two days.
A video streamed on Facebook Live by Mr Castile's girlfriend, Lavish Reynolds, showed him bleeding to death as she explained that they had been pulled over for a broken tail light and the 32-year-old was shot as he reached for his wallet.
