Condolences and fond memories flooded social media Monday morning following the death of Dustin Diamond, the actor best known for his role as lovable nerd Samuel “Screech” Powers in ‘90s sitcom “Saved by the Bell.” Fans and fellow actors — including former costars Mario Lopez, Tiffani Thiessen and Mark-Paul Gosselaar — were among the first to react to Diamond’s death, which came a few weeks after he completed his first round of chemotherapy treatment after being diagnosed with small-cell carcinoma. Diamond was 44. “The fragility of this life is something never to be taken for granted,” Lopez wrote on Twitter, before offering prayers for Diamond’s family.