PICTURED: Hydrology professor shot dead by former student, 46, who 'stormed science building at the University of Arizona and opened fire'

• Thomas Meixner, 52, was head of the UA's Department of Hydrology and Atmospheric Sciences was shot and killed on campus on Wednesday
• The professor had been praised for his research on water quality and climate change and his death was called a 'crushing loss to the water community'
• Murad Dervish, 46, a former student was taken into custody after the shooting
• Police responded to the shooting at the University of Arizona campus' John W. Harshbarger building around 2pm on Wednesday 

A University of Arizona professor was gunned down on campus Wednesday when a former student who was not allowed to be on the property allegedly made his way into the science building and opened fire.

Thomas Meixner, 52, was head of the UA's Department of Hydrology and Atmospheric Sciences and had been noted for his research on water quality and climate change. 

Meixner was rushed to the hospital after being shot around 2pm. He was pronounced dead in the emergency room.

The suspected gunman was identified as former student Murad Dervish, 46, according to UA Police Chief Paula Balafas, who gave an update following his arrest just after 5pm.  

Balafas said the victim was a professor in the Department of Hydrology but said she would not be releasing his name. 

The professor's identity was first confirmed by the Tucson Sentinel and tributes have since poured in for the educator, with one person calling his death a 'crushing loss to the water community' and another declaring it a 'sad day for science.'

Police say the on-campus shooting happened just after 2pm inside the John W. Harshbarger Building - which houses the Department of Hydrology and Atmospheric Sciences.

'Someone recognized the student and knew that he was not allowed inside the building,' Balafas said. It was not revealed why Dervish was not allowed inside the building. 

The campus was under lockdown for over an hour as police searched for the suspect, who was located off-campus. 

'I don't know what the suspect's issue was in this case, but if you see something, don't just say something but do something. If you know someone struggling with mental health issues or anger issues, please reach out,' Balafas said. 

Balafas said that campus police first received a call from inside the building who recognized the ex-student as someone who was not allowed to be there. 

The caller requested the suspect be escorted out. Within a few minutes, another caller reported a shooting inside the building. 

The campus remained on lockdown and students and staff were asked to shelter in place for more than an hour as police searched for a gunman.

The suspect was identified and sought after by police but had fled the campus. Just after 5pm, the suspect was taken into custody During a traffic stop just outside Gila Bend by the Arizona Department of Public Safety.

Video and photos posted to social media show the scene outside the building as emergency officials carry a man out to a gurney and into a waiting ambulance. 

The victim - later identified as Meixner - was taken to Banner-University Medical Center, where he was pronounced dead.

'It's a tremendously tragic event. We feel so incredibly bad for the professor's family, friends and colleagues,' Balafas said. 'Our hearts really just go out to them. It's definitely a tragedy.' 

Tributes flooded in for Meixner, whose research focused on understanding the hydrology and water quality of desert rivers. 

Meixner had taught at UA since 2005 and became department head in 2019. He leaves behind a wife and two sons, the Sentinel reported. 

Kaveh Madani, a professor in New York, tweeted, 'A sad day for our field! A sad day for #science!' 

Another user said: 'Crushing loss to the water community. Tom was highly respected for his research in water harvesting. Mourning this senseless tragedy tonight.'

Dr. Laura Meredith tweeted how she and Meixner submitted a grant last week.

'I am in complete shock. We just submitted a grant last week. I can't think of a nicer or more supportive colleague/mentor/human. This is devastating and senseless. How sorry I am for so many people now in pain.'