A man has been arrested by police investigating the shooting of a woman officer during a robbery at a pub.
Searches are under way for a second man
Police dog handler Katie Johnson, 29, had been sent to a reported raid at the Hospital Inn in Bamber Bridge, Preston.
The Pc received 12 pellets in her leg when she was shot by a man wearing a balaclava, after colleagues ordered him to drop his weapon as he tried to flee.
Searches are under way for a second man in what police say is "an incredibly serious situation".
Lancashire Police's Acting Assistant Chief Constable Jerry Graham said: "This was an incredibly violent incident - the level of violence was extreme."
The two robbers fled down the nearby Trans Pennine Railway line, which has been closed while police search the area.
A man who worked at the pub was also injured in the robbery but was not shot, police said.
Police were called to the pub on Brindle Road just before 0830 GMT after reports intruders were inside.
A number of officers were deployed and were confronted by a man with a gun coming out of the pub.
A police dog handler ordered him to drop the weapon, which he refused to do, police said.
He then fired at Pc Johnson. She suffered wounds to the top of her leg and has been taken to the Royal Preston Hospital.
Lancashire Police said a man had been arrested "close to the scene" and searches were under way for a second.
Extra officers, including armed officers, dog handlers and the force helicopter have been deployed.
Assistant Chief Constable Jerry Graham, from Lancashire Constabulary, said: "This is an incredibly serious situation where a police officer has been shot at and, whilst we have arrested one man we may still have an offender in the area.
"We are currently conducting a number of searches and have had to cordon off the area which may cause disruption to people.
"However, this is a live operation and public safety is our primary concern and we would ask people to be patient and cooperate with the police."
Pc Johnson is the latest female officer to have been shot while on duty.
In November 2005, Sharon Beshenivsky, 38, was shot dead as she tried to stop an armed robbery on a travel agency in Bradford.
Three months later, trainee officer Rachael Bown needed emergency surgery after being shot in the abdomen while attempting to apprehend a suspected burglar in Nottingham.