A fifth man has been arrested after a university student was left with life-threatening injuries following a street attack in Ceredigion.
Ifan Richards Owens, 19, was found unconscious on High Street, Aberystwyth, in the early hours of Sunday after the assault.
A 24-year-old man has now been arrested on suspicion of assault.
Three other arrested men have been released under investigation while a 19-year-old has been released on bail.
Det Ch Insp Anthony Evans, of Dyfed-Powys Police, said: "We are still trying to find the adult male who administered first aid to Ifan before emergency services arrived.
"We would really like to speak to him to see if he can help in any way with our investigation.
"Anyone else who has not yet come forward who was in the High Street area between 00:45 and 02:30 and has information or footage of the incident, please get in touch."
Mr Owens, a second-year student at Aberystwyth University, was initially taken to Bronglais Hospital, Aberystwyth but was later transferred to Cardiff's University Hospital of Wales.
Police said he remains in a critical condition.
His family said they have been "overwhelmed" with the support shown for their "kind and gentle" son.