A wannabe Islamist killer used a paintballing session to train for jihad as he plotted to join terror groups fighting in Syria, a court has heard.
Ahmedeltigani Alsyed, 20, pleaded guilty in January to one count of engaging in conduct in preparation of terrorist acts.
Between November 25 2016 and February 20 2017, the Sudan-born extremist from Hounslow, west London, conspired in a secret communication channel to fight in the Middle East, while building his strength at a gym and attending a paintballing event for training, prosecutors claimed.
He told a friend in an encrypted Telegram message that "I just want to do martyrdom operations", Woolwich Crown Court was told during a sentencing hearing on Tuesday.
He was also convicted of disseminating terrorist material, including execution videos and bomb-making guides, and possessing information likely to be useful to a person committing or planning acts of terrorism.
His brother Yousif Alsyed, 18, was convicted of one charge of engaging in conduct in preparation of terrorist acts and one of disseminating a terrorist publication, but will be sentenced at a later date.
Prosecutor Annabel Darlow QC told the court: "The brothers had a shared aspiration to travel to Syria to join and fight with fundamentalist jihadi groups and, ultimately, to die fighting in the belief that in death they would achieve martyrdom."
The defendant is expected to be sentenced on Tuesday.
Earlier, Ms Darlow said the brothers had joined their cousins for a paintballing session at Blind Fire paintball facility in Surrey on September 3 2016.
"The Crown say in the midst of messaging, in the midst of these activities, it really could be no idle coincidence," she added.
A video of the paintballing session was played to the court, showing the older brother playing up to the camera.
Dressed entirely in camouflage, he raises one finger - which the prosecution said mimicked a pose struck by Islamic State fighters - and says: "This is a message to everyone; if we do not come back safe and sound, look after our families, that's all."
But, giving evidence at a Newton Hearing on the paintballing incident, the defendant said: "I was joking.
"Obviously there were men holding big guns and the night before we watched videos of people screaming and crying (during paintballing) and I was terrified."
Around the same time he joined a gym, Xercise4Less in Hounslow, making regular visits until February despite concerns he should not go because girls used the facility and pop music was played.
He said to a facilitator purporting to be from Islamic State on Telegram: "I was chatting to my friend yesterday he told me you getting fit for hijra coz there they do mad training so that is a good reason to go back to the gym."
Their plan was foiled when the younger brother was referred to police by his concerned school in 2016 and further action was taken by Prevent.
They had been part of a secret Telegram chat group called Peace in which five young men shared IS beheading videos and urged each other on.
Two teenagers, Mohammed Ali, 18, and a 17-year-old who cannot be named for legal reasons, were also part of the group. They were both jailed in January for attempting to join Islamic State in Syria.
The Alsyed brothers went on holiday to Egypt with family and in August 2016 were subject to a port stop on their return.
When police learnt Ali and the teenage accomplice had booked flights in February 2017, they executed a search warrant on the brothers' address and their phones were seized, with the pair both arrested in a further raid six days later.
A trove of incriminating evidence was found on the devices, including contact on Yousif's phone with a facilitator in Yemen about "potential travel to Libya or Syria for the purpose of joining Daesh", the prosecution said.
Among the material uncovered by police were messages expressing a desire to die a martyr for extremist Islamic groups in the Middle East.
One message sent by Ahmedeltigani said: "I want to be istshadi (a martyr) I want every bit in my body to be destroyed."
Yousif said in a separate message to a man known only as N in April 2016: "My plan is to die for Allah, to be a martyr."
He discussed at length with N the route he would take to the Syrian border.
His brother, meanwhile, asked a friend how big the queue was to become a martyr, the court was told.