Dozens of armed police including counter terrorism officers descended on the college after shots were fired at the College Road site, police said.
And now a police chief has praised the staff for putting themselves in harms way to protect others.
Chief Inspector Shane Baker, of the Crawley Neighbourhood Policing Team, said: “I’d personally like to thank everyone who helped to quickly bring this incident to a safe conclusion, especially the two members of college staff whose heroics have not gone unnoticed.
“They put themselves in harm’s way in order to protect their students, fellow employees and the wider public, and I am hugely grateful for their quick-thinking actions.”
During the horrifying incident blank shots were fired – which did not hurt anyone – but the two staff members suffered minor injuries not caused by gunshots, said police.
Police were first called to the scene at 3.10pm and within minutes dozens of police vehicles including the helicopter were on the scene.
Officers found the suspect detained by two college employees; a teacher and a member of support staff.
A police spokesman said: “A blank firing handgun and a knife were seized, and at 3.20pm an 18-year-old man from Crawley was arrested on suspicion of firearms offences. He remains in custody at this stage.
“Pupils and staff were evacuated to a safe space while police carried out a search of the buildings, assisted by the Explosive Ordnance Disposal. West Sussex Fire and Rescue Service and South East Coast Ambulance were also in attendance. Nothing suspicious was found.
“Officers also conducted a search at an address in Barton Walk, Crawley, in connection with the incident.”
CI Baker added: “We are treating this as an isolated incident which was not terror-related, and while we are not seeking anyone else in connection with it, we will continue to provide a high visibility police presence in the area for community reassurance.
“We are also working with the college and the local authority to manage the welfare and wellbeing of those involved – including students – who will have been understandably shocked by this experience.
“Our enquiries are ongoing into this criminal investigation, and anyone with any information is urged to report it online or call 101, quoting Operation Reset.”
Crawley College is assisting Sussex Police with its investigation, and has confirmed that the college will be closed until at least Thursday April 29.