'Heart is shattered': Girlfriend and friends share tributes to slain Aussie brothers

The girlfriend of one of the Perth brothers suspected to have been murdered in Mexico has shared emotional tributes to him, saying her "heart is shattered into a million pieces".

Australians Callum and Jake Robinson and their American friend Jack Carter Rhoad were found dead at the weekend after disappearing in the northern Mexico state of Baja California.

San Diego resident Emily Horwath, who was in a relationship with Callum, shared a series of emotional tributes to the 33-year-old on social media.

READ MORE: Israel tells Palestinians to evacuate ahead of expected assault

"My heart is shattered into a million pieces," she said.

"I don't have the words right now.

"You are one of one. I will love you forever."

Her words, photos and videos of the pair together were part of a flood of tributes to Callum and his 30-year-old brother shared online.

Jena Aro said the world was "an evil place".

"But I won't let it stop me from spreading the kindness you brought into this world," she wrote, on Instagram.

Horwath described Aro as the couple's "permanent third wheel", saying she loved the way Callum treated her best friends as his own.

READ MORE: Messages reveal 'radicalised' Perth teen's 'jihad' plans

"Truly one of the most beautiful and loving souls," another friend of Callum's wrote.

"The world lost one of its kindest silliest and most genuine of souls this week," another message said.

Callum was living in San Diego, having played professional lacrosse in the US.

READ MORE: Bondi stabbing survivor says smiling doctor helped her recover

Jake was visiting his brother before taking up a new job at a hospital in Geelong.

The trio were alleged to have been killed after fighting back against people trying to steal the tyres on the ute they were travelling in.

The men's bodies, which were found 10 metres down a well south of the city of Ensenada, were officially identified after their parents, Martin and Debra Robinson flew to Mexico.

Authorities claimed they'd been shot through the head, execution-style.

Three abandoned tents were also discovered along with the remains of a campfire in the remote beachside area.

The ute was found on a farm, burned out.

Three Mexicans, Jesús Gerardo Garica Cota, alias El Kekas, his partner Ari Gisel García Cota, and his brother Christian Alejandro Garcia, have since been charged with forced kidnapping.

Sources tell 9News it is believed the trio will be charged with murder in the coming days.

READ MORE: Urgent search for two brothers after fatal stabbing in Melbourne

READ MORE: Chinese jet intercepts Australian Navy helicopter in 'unsafe' move

A photographer friend of Callum, Randy Dible, said he was almost going to join the trio on the trip, after recommending them where to go and drawing "a map on a napkin".

He said his "friend and neighbour" Callum bought a photo print, and asked him where in Mexico he should go with his brother.

"I told him about Santo Tomas Valley and go camp in the Oak Groves at the Ahusco where my grandparents brought me camping every year when I was a boy and I brought my friends and family there through the decades," he wrote on Instagram, referring to an area close to where they were found dead.

"Then told him to go to La Bocana at the end of the valley where there's great fishing and there's a wave to surf.

"I drew him a little map on a napkin. He asked me if I wanted to go.

"At first I said yeah, it sounds like fun but I turned him down when I found out I had to work."

Dible described his friend as "really great guy and champion Lacrosse player and surfer."

Callum previously studied at Stevenson University in Maryland, where the lacrosse team held a minute's silence for the man they called "Big Koala".

"Callum will be remembered for his infectious spirit and larger-than-life personality," the university said.

"With his beautiful long hair and charming smile, he truly embodied the nickname 'big koala'— warm, friendly, and always there to lend a helping hand.

"Though he may be gone, Callum's legacy will live on in our hearts forever."

A fundraiser has gathered more than $280,000 for the brothers' family.

Donations have been made by friends and family as well as patients of Jake.

"Such an unimaginable tragedy," one person wrote.

"Hearts, not just here in Western Australia, are truly broken," another said.

Baja California Attorney General Maria Elena Andrade Ramirez met with parents of the victims on Sunday and "reaffirmed the institution's total commitment to continue the investigation into these unfortunate events until those responsible are fully prosecuted by the law", she said.

The area has been plagued by drug cartel violence in recent years, though it rarely occurs in tourist areas like Ensenada.

The latest suspected murders sparked outrage in the surf community of Ensenda, where about 500 people marched on Sunday to call for justice and better security.

While parts of Mexico are established tourist destinations, violent crime including kidnapping and human trafficking plague parts of the country, particularly in border areas.

Mexico's homicide rate is among the highest in the world, and more than 100,000 people remain missing in the country.

- reported with CNN.