Photo of Yuan Yuan sending off her brother on her Weibo account. [Photo from Weibo]

Yuan Hai is one of the 17 firefighters who lost their life while carrying out a rescue mission after explosions rocked the port city of Tianjin on Wednesday night.

Among all the confirmed fatalities, he is the youngest one.

"He's turning 18 next month," his sister Yuan Yuan said. "I remember it clearly that he joined as a firefighter on Sept 18 last year. And we were so proud of him."

His sister's Weibo account, a popular social network in China, shows pictures the day she sent off her brother to join the army.

She wrote: "My brother will be much more handsome in that uniform when he's back in two years. Our whole family is proud of him...We kept smiling but can't help crying for the parting when his couch set off."

Yuan Hai and his family live in Yong'an township, Zhongjiang county, Deyang, Southwest China's Sichuan province.

Yuan Yuan knew her brother belonged to the rescue team that was carrying out the operation at the blast site. She began worrying and kept calling him since Thursday morning.

But she wasn't able to reach him.

She felt more anxious when she heard that firefighters had lost their lives in the mission. Only thing she could do was keeping calling her brother.

On Thursday night, the family received the news. "I need to go to see him for the last time," her father said.

Yuan Hai's father and his uncle set off on their trip to Tianjin.

His sister couldn't handle the news and expressed her grieve on Weibo: "It cannot be real. My dearest brother...how can you be so cruel to leave our parents to me? We don't want you to have big achievement but you being safe and sound...we want you back."

After she posted her comments, Internet users flooded her Weibo account with their messages of support. Some said "Your brother is a hero and a brother to us all, while others said "Allow me to call you 'sister' and please be strong."

More than 166,000 comments and 260,000 reposts on her Weibo echoed her love and grieve to her brother.

The family still hasn't informed the mother about the passing away of her son as they are not sure how she would handle the news at this old age.

"I wouldn't dare to tell my mom about it," his sister said. “I really don't know how to tell her.”