Teenager, 17, is arrested over the death of a tradie, 26, who was allegedly stabbed in the heart with a broken bottle while trying to defend his girlfriend outside a pizza shop

A 17-year-old has been arrested after a tradesman was allegedly stabbed in the heart with a broken bottle while defending his girlfriend outside a pizza shop.

Cam Smith, 26, was found with life-threatening injuries near Seaford train station, southeast of Melbourne's CBD, at 6.55pm on Wednesday.

Mr Smith, from Langwarrin, near the Mornington Peninsula, was treated by paramedics at Station Street but died at the scene. 

On Thursday afternoon, a 17-year-old man from Frankston was arrested and is assisting police with the investigation. 

Cam Smith (pictured above), 26, was allegedly stabbed to death by a group of random people outside Seaford train station, south of Melbourne's CBD, on Wednesday evening

Detectives are still looking for two males and a female who they believe can assist in the investigation. They are urging the trio to come forward and contact police. 

Mr Smith has been described as a 'go getter' with a 'heart of gold' who died protecting his girlfriend.  

'He wanted a family and his life was snuffed out in a matter of minutes,' his father Mike Smith told 3AW on Thursday.

The 26-year-old carpenter was protecting his girlfriend after a group approached them, the devastated father explained.

'He went to defend her and a bottle was broken, and in that fight he was stabbed in the heart and died fairly quickly.' 

It is understood Mr Smith had been getting a pizza with his girlfriend before the group allegedly began verbally attacking Mr Smith's girlfriend and he defended her 

Flower tributes have been left (pictured above) near Seaford train station to honour Mr Smith

'He had everything to live for, he was a go-getter, hard worker, he had a heart of gold, he would help anyone, anytime, he was just a fantastic kid.'  

Mike said the rest of their family and Mr Smith's girlfriend were 'absolutely distraught'. 

'You hear stories of people losing their loved ones to crimes and lives taken and you feel sorry for them and your life goes on,' he told 7News.

'You don't really know what the family is going through... now I do.'

The incident has highlighted ongoing Victoria Police concerns about crime involving knives and edged weapons. 

Victoria Police Chief Commissioner Shane Patton said he was particularly concerned about knife crime in the state.

No arrests have been made and his alleged killers remain on the run (train station pictured)  

'Stabbings, knife attacks something I am terribly concerned about at the moment,' he told 3AW.

'I've been having that monitored - there are intelligence assessments for the last six months.

'We've seen significant rises in the use of edged weapons and knives and it's a real concern for us.'

Mr Patton said there were a number of witnesses to Wednesday night's stabbing.

'There are a number of leads. It appears there was an altercation and that's led to a male being stabbed, which is a horrible outcome,' he said.

Mr Smith was described as a 'fantastic kid' with a 'heart of gold' (tributes pictured above) 

'We will identify the offenders, there's no doubt about that.

'They would be better off coming forward and handing themselves in.'

Homicide Squad detectives spent the night investigating the scene and the four suspects are still on the run.  

Shocked witnesses, including 16-year-old Dylan, claim to have watched the confrontation unfold. 

'There was a man with a glass bottle and he walked over to another man and started fighting with him,' he told the Herald Sun. 

Homicide Squad detectives investigated the crime scene (officers pictured on Thursday) 

 Victoria Police (crime scene pictured) are reportedly searching for three men and a woman

'I then saw the man fall to the ground. There was blood everywhere, it was really bad.' 

Another onlooker said he was left 'traumatised' after watching the attack on the 26-year-old.

'He was choking up blood and asking for help, it was terrible,' he explained.  

Witnesses also took to Facebook to share their accounts, claiming emergency services were forced to conduct CPR on Mr Smith 'for a good 10 minutes'.        

The investigation remains ongoing and Victoria Police have urged anyone with information to contact Crime Stoppers. 

Homicide Squad detectives (police pictured on Station Street) are investigating the circumstances surrounding the attack and witnesses have been urged to come forward